Week 3

 Week 3 PIR sensor connection

This week we tried to build the whole circuit according to the circuit diagram which is shown in Fig.1,  and use PIR sensor to detect human movement and output signal. 


Figure 1 The PIR sensor diagram

Since the Fig.1 circuit diagram is a little bit complex, we simplify the circuit, which is shown in Figure 2.

Figure 2 Simplified circuit diagram of PIR

Firstly, we built the first part, which is amplifier 1. We redesign the circuit and try to delete the Arduino board to make the circuit more simple. Resistors and capacitors are also used to protect all the elements. However, in the first few attempts, we cannot sketch the output signal. Nothing useful was displayed on the oscilloscope.

                                                        Figure 3 PIR connection of the first part

In our assumption, we think it might be because of the component problems and the connection problem that happened in the physical connection.  To solve this problem, we first tested all the circuit components for damage. And then we tried to find whether there are some problems in connecting.  Finally, we found that we forgot to adjust the oscilloscope. After solving the problems, the PIR sensor will output the change of the waveform on the oscilloscope, which is shown in Fig.4 when it detects the motion of people.

Video1 The waveform change

Figure 4  The waveform change of PIR sensor

According to Fig.4, the output signal is basically the expected or theoretical signal which is shown in Fig.5.
We also found that both the distance and the speed of motion affect the waveform. In general, the closer you get to a sensor the more sensitive it is, the greater amplitude of the signal. As the speed of movement increases, the frequency of signal changes increases. 

Next week, we will finish the PIR circuit and package our circuit.
Figure 5 The theoretical signal 



评论

发表评论

此博客中的热门博文

Week 1

图片
 Week 1 Simulation 1.1 PIR simulation This week we checked all the ordered components and equipment. We plan to build an infrared automatic door making use of PIR sensor to detect human motion. Before building the circuit in reality we firstly built an analogous circuit through software such as Multism to see how it works which contains a PIR sensor. However, in the Multisim software, there is no PIR sensor component, power supply, which can generate sinewave, is used to replace the signal generated from the PIR sensor. Figure1 PIR sensor simulation After finishing building the circuit in Multisim software, we simulate the circuit part by part. The first part is the amplifier, which is used to amplify the input signal. This is shown in Fig.2, and the result is shown in Fig.3. Figure 2 The first part of the circuit Figure 3 The result of the simulation for the first part According to Fig.3, the blue signal is the output signal and the green signal is the input signal, and the input ...
阅读全文

Week 4

图片
Week 4 Finish building the PIR circuit and package. Last week, we have finished the first amplifier of the PIR circuit, and this week, we built the second amplifier and comparator which is shown in Figure 1. Figure 1 (PIR sensor circuit) Meanwhile, we connected a LED light to the output of the comparator. When nobody moves in front of the PIR sensor, the light will be turned on, and when the human motion is detected the LED will flash which is shown in the video. We infer that when no one passes through the PIR sensor, there is always a DC signal in the circuit because we used a power supply to supply DC voltage to the amplifier. The reason for this phenomenon is that the final part is Op-amp Comparator, which is used to digitalize the signal, and we choose the non-inverter comparator circuit.   When there is no input signal, the output signal is the reference voltage, if there is an input signal which is similar to a sinewave, which makes the output signal up and down like a squar...
阅读全文